#include <iostream>
using std::cout;
using std::endl;

namespace MySpace
{
extern int num;

extern int add(int x = 1,int y = 0);

extern double add(double x,int y);

extern double add(int x,double y);

extern int add(int x,int y,int z);

}//end of namespace MySpace

void test0(){
    using MySpace::num;
    using MySpace::add;
    cout << num << endl;
    cout << add() << endl;
    cout << add(3) << endl;
    cout << add(3,4) << endl;
    cout << add(7.5,8) << endl;
    cout << add(4,7.9) << endl;
    cout << add(1,2,3) << endl;
}

int main(void){
    test0();
    return 0;
}
